Upgrading vehicles questions

How hard is it to engine swap ect? My dad has a shop that fits like 2 vehicles in it, along with an engine lift so I have all the tools to do it along with my dad who knows how to do it, I'm thinking of pimping out a older vehicle, but I will want a newer engine in it along with a transmission probably, anything else I might wanna fix in a older vehicle? This would be a big time consumer correct?